American Scientist

Carl Sagan: A Life. Keay Davidson. 512 pp. John Wiley and Sons, 1999. $30.

Carl Sagan: A Life in the Cosmos. William Poundstone. 449 pp. Henry Holt, 1999. $30.

Carl Sagan had an enormous impact on planetary science and science popularization. His successes and excesses will likely be debated for many years. Three years after Sagan's untimely death from cancer, we have two fine biographies to remind us of his achievements.

Both books contain the full sweep of Sagan's impact as a scientist and popularizer; the differences between them are in style and emphasis. William Poundstone's Carl Sagan: A Life in the Cosmos is stronger on the central scientific issues in Sagan’s career. For example, Poundstone gives an excellent description of the debates where Sagan stood at center stage: the evidence of life elsewhere in the solar system and the effects of nuclear war on global climate. Keay Davidson's Carl Sagan: A Life is richer in anecdotes and quotes. Davidson’s discussion of Sagan’s personality is particularly insightful.

Sagan grew up in New York, his self-confidence nurtured by a protective and doting mother. He became interested in astronomy in the manner of many a curious child, as an avid reader of science fiction. As a teenager, he stunned the patrons of a fancy restaurant by blurting out, "I tell you, Jesus Christ was an extraterrestrial!" His Utopian beliefs may have been grounded in a childhood visit to the 1939 New York World's Fair.

Davidson makes the point that Sagan's polymath grasp was encouraged by the challenging (and now obsolete) curriculum of classics and humanities he encountered as a student at the University of Chicago. He made his mark quickly, with a dissertation that predicted Venus to be an infernal planet because of the greenhouse effect. Throughout his career, Sagan was drawn to study situations of low probability but high potential impact: the detection of extraterrestrial life, the effects of nuclear war and terrestrial catastrophes in general.

Even as a graduate student, Sagan's mixture of hubris and enthusiasm fueled a rapid ascent. He befriended Nobel laureates and impressed most of his colleagues as a quick, if occasionally glib, thinker. As a theorist, Sagan preferred to estimate outcomes in the manner of a Fermi problem rather than subject problems to the austere formalism typical of colleagues like Chandrasekhar. As Davidson makes clear, the rise that seemed effortless was in fact driven by a ferocious work ethic and a ruthless competitive streak. Sagan was a dedicated careerist who planned every stage of his ascent.

Poundstone gives an excellent account of the Viking missions and of the complex issues involved in the experiments to test for living organisms. Sagan was indefatigable in raising money for space science and in explaining the subtleties of planetary geology and chemistry to as many people who would listen. He was pivotal to the funding and subsequent success of the Voyager and Pioneer missions.

Poundstone also provides a nice summary of the nuclear-winter debate, which was emblematic of Sagan’s growing politicization. Sagan's stance was controversial because he chose to underplay the ambiguities of early computer models of nuclear war in order to lobby for arms reduction. Yet there is clear evidence that Sagan—with his Soviet connections and his high-powered lobbying—contributed to the thaw that ended the Cold War. Sagan's political leanings had a downside. After he had snubbed invitations to the Reagan White House three times, Sagan's advocacy of a manned Mars mission was enough to make Reagan balk at the idea.

In both biographies, we learn about Sagan's private life. Davidson has some very acute observations on Sagan's behavior and personality. The picture that he paints is not a pretty one. Sagan's first marriage, to noted biologist Lynn Margulis, suffered from his neediness and blinkered obsession with his career—she referred to it as "a torture chamber shared with children." He was estranged for long periods from three of his five children. His first two wives were not the only people to feel the icy edge of his arrogance. Even when he made his third and happiest partnership, with Annie Druyan, it came at a cost: When he met her, she was the fiancée of his good friend Timothy Ferris.

Sagan was a man-child whose well-burnished ego and imperious style made him insufferable at times. The Apple Corporation once asked for his permission to use his name as a code-name for one of its lines of computers. He refused, and Apple internal memos began to use the code-name BHA (reputed to stand for Butt Head Astronomer). He sued for libel, and the case was swiftly thrown out of court. This difficult man was hidden to the millions who saw only the suave and compelling TV performer.

Even as a prolific and influential scientist, Sagan's public success was without precedent. "Cosmos" was the highest rated public-TV series ever, seen by over 500 million people in 60 countries. (The Beetle is back, disco is in and bad '70s sitcoms never went away, so the thought of Carl Sagan in his turtlenecks and corduroy jackets is a comfort to us all.) Later, he was a regular on the "Tonight Show" and a Hollywood insider from his work on the film Contact.

A number of Sagan's colleagues felt that his immense fame far outstripped his talents as a scientist. These sentiments were mostly based on envy, and they badly missed the point. Sagan was a compelling advocate for science, and all scientists benefited from his efforts. He was put up for membership of the National Academy of Sciences, but the nomination was shot down because of distaste for his efforts at popularization. This parochial and mean-spirited action is a large black mark in the history of that august body.

Sagan was a bundle of contradictions. He once said: "If a scientist identifies his self-esteem too closely with the theories he proposes ... it is scientific suicide. The theory and the person are not the same." Yet Sagan was clearly and emotionally attached to the idea of life in the universe. He speculated with gusto about extrasolar civilizations and creatures that could "float" in the Jovian atmosphere. Even as the Viking experiments closed the door on sizable Martian life forms, Sagan held out for the existence of hard-shelled bugs.

The "poet of exobiology" was swayed by the fecundity of the universe. With so many stars and sites for life, how could we possibly be alone? The central objection to SETI, the Search for Extra-Terrestrial Intelligence, has always been that it represents an unfalsifiable hypothesis. Sagan used to infuriate his critics with his finely honed use of the double negative: "We have seen nothing that can rule this out." In this way he could suggest outlandish ideas without actually asserting them. (His dazzling conjecture was then placed in counterpoint to the dull accumulation of data by Popperian scientists.) He wanted to have it both ways, using the Drake equation to argue for the ubiquity of life, then downplaying it as an "entertainment." Ironically, as quoted by Poundstone, Sagan himself came close to pinpointing the nature of the spiritual appeal of SETI: "In a scientific age, what is a more reasonable and acceptable disguise for the classic religious mythos than the idea that we are being visited by messengers of a powerful, wise, and benign advanced civilization?"

Sagan had a playful side as well. He provoked his Viking colleagues into using valuable payload space for a camera by pointing out that their microbial experiments might miss larger life forms, like Martian polar bears. When he researched animal intelligence, he once had to fend off sexual advances from the dolphin that played TV’s "Flipper." He claimed to have had many of his most creative thoughts while high; Davidson provides excerpts from Sagan's "pot diaries."

Contradictions appeared in Sagan's personal life as well. He was a highly visible feminist who never lifted a finger around the house and paid scant attention to the needs of first-wife Margulis, whose career would one day rival his own. He could be fiercely loyal to his friends and students, but he fell out with his best friend over a slight to the friend's son, and his stubborn pride would not allow for a reconciliation, not even on his deathbed. He did, however, face his harrowing ordeal with bone-marrow cancer unflinchingly and with his trademark optimism intact.

I recommend each of these biographies highly. For a direct narrative with lots of scientific details, choose Poundstone. For an entertaining (and occasionally overheated) writing style and more psychological insights, choose Davidson. Both contain copious notes, and Poundstone offers a selective bibliography. Both writers do a fine job of conveying the life of a highly influential scientist—Sagan was by turns charismatic, moody, competitive and expansive.

Was Carl Sagan a hero? He was too deeply flawed as a person, and occasionally as a scientist, to be truly heroic. However, Sagan never lost his sense of childlike wonder in the universe, and he captured the interest of millions of people for whom science was a closed book. All those of us who pursue our intellectual interests with public money are indebted to him for inspiring and educating so many of the people who actually pay the bills.